Potamonautes flavusjo, Daniels & Phiri & Bayliss, 2014

Daniels, Savel R., Phiri, Ethel E. & Bayliss, Julian, 2014, Renewed sampling of inland aquatic habitats in southern Africa yields two novel freshwater crab species (Decapoda: Potamonautidae: Potamonautes), Zoological Journal of the Linnean Society 171 (2), pp. 356-369 : 363-366

POTAMONAUTES FLAVUSJO SP. NOV.

( FIGS 6 , 7A–C , 8A–C )

Holotype: One male specimen (SAM A 48203), Verloren Vallei Nature Reserve (site B), 2000 m a.s.l., 25°20′19″ S, 30°07′32″ E, Mpumalanga province of South Africa, collected on 27 June 2013 by Savel Daniels, Fawzia Gordon, and Piet Makuwa.

P. suprasulcatus ; however, phylogenetically these two species are distantly related. Potamonautes bellarussus sp. nov. formed a distinct cladem whereas P. suprasulcatus was sister to P. lirrangensis . In addition, P. suprasulcatus has a sharp carpal tooth on the carpus of cheliped and a second carpal tooth smaller spine, with no other teeth behind it, whereas a tooth is present in P. bellarussus sp. nov. In addition, P. bellarussus sp. nov. and P. suprasulcatus are ecologically distinct, with P. bellarussus sp. nov. living in Paratype: Six male and one female specimens, (SAM A 48204) Verloren Vallei Nature Reserve (site A), 2018 m a.s.l., 25°18′25″ S, 30°08′25″ E, Mpumalanga province of South Africa, collected 28 June 2013 by Savel Daniels, Fawzia Gordon, Mr Mkwana, and Gerhard Diedericks.

Additional material examined: Six females (SAM A 48206), with the same locality and collection information as the holotype. One female (SAM A 48207), Verloren Vallei Nature Reserve (site A), 2016 m a.s.l., 25°18′25″ S, 30°08′25″ E, Mpumalanga province of South Africa, collected on 27 June 2013 by Savel Daniels , Fawzia Gordon , and Piet Makuwa. One male (SAM A 48208), Verloren Vallei Nature Reserve (site C), 2065 m a.s.l., 25°17′18″ S, 30°09′18″ E, Mpumalanga province of South Africa, collected on 28 June 2013 by to dull yellow upon preservation in absolute ethanol. Anterolateral margin of carapace smooth, lacking dentition, exorbital tooth low but well defined ( Fig. 7A– C ). Ventral carapace surface and ventral chelipeds light yellow .

Savel Daniels, Fawzia Gordon, Mr Mkwana, and Gerhard Diedericks. One female (SAM A 48209), Elandshoek, 1987 m a.s.l., 25°22′33″ S, 30°06′45″ E, Mpumalanga province of South Africa, collected on 28 June 2013 by Savel Daniels, Fawzia Gordon, and Gerhard Diedericks. Nine specimens (SAM A 48205), Miss Chrissie’s Country House Farm, Chrissiesmeer, next to Lake Chrissiesmeer , 1665 m a.s.l., 26°17′33″ S, 30°13′24″ E, Mpumalanga province of South Africa, collected on 30 June 2013 by Savel Daniels and Fawzia Gordon. Five specimens (SAM A 48210), Iona Farm , in the Lake Chrissiesmeer district , 1648 m a.s.l., 26°13′46″ S, 30°10′40″ E, Highveld of the Mpumalanga province of South Africa, collected on 2 July 2013 by Savel Daniels , Fawzia Gordon , Hannes Marais, and Ursula Franke .

Diagnosis: Carapace highly vaulted, postfrontal crest margin, periopods, and chelipeds bright yellow, fading Description: See Table 3 for measurements of the holotype. Live specimens of P. flavusjo sp. nov. have a distinct yellow postfrontal crest band and dull mottled yellow marked cephalograstic and anterolateral margin region. Chelipeds and ventral surface of periopods light yellow, dorsal surface of the periopods light brown ( Fig. 7A, B, C ). Colour fades upon preservation. Carapace distinctly vaulted (CWW/ CH = 2.33) narrow posteriorly (CWP/CL = 0.51). Anterolateral margin smooth. Postfrontal crest deep, well defined, and curves forward medially. Exorbital tooth small, moderately sharp. Urogastric and cardiac grooves defined. Sternites 1 and 2 fused. First suture between sternites 2 and 3 complete. Second sternal groove between sternites 3 and 4 complete. Third maxillipeds fill the entire buccal frame, except for respiratory opening. Mandibular palp two segments, terminal segment undivided, sense tuft of setae on posterior surface of flange. Chelipeds generally unequal, in the holotype the right cheliped is broken off. Dactyli armed with 18 small cutting teeth. Carpi of chelipeds possess one prominent tooth and two small teeth. Pereopods slender, periopod 3 is the longest, periopod 5 is the shortest. Dorsal margins of pereopods with fine sharp bristles, dactyli ending in sharp points, margins possessing spine-like bristles. Pleopod 1 (gonopod 1), terminal segment short, 0.24 times length of subterminal segment, terminal segment curves away from midline when viewed posteriorly, widest at base ending in point. Subterminal segment tapers distally ( Fig. 8A, B ). Pleopod 2 (gonopod 2) terminal filament-like, 0.5 times the length of subterminal segment ( Fig. 8C ).

Distribution: Endemic to the Highveld region in the Mpumalanga province of South Africa, where the species occurs exclusively in vlei (wetland) areas next to small streams where they burrow into peat soils. Burrows are always covered by grassy pools and reed beds.

Remarks: Although frequently collected sympatrically with P. sidneyi , P. flavusjo sp. nov. is genetically and morphologically distinct. Phylogenetically, P. flavusjo sp. nov. is sister to P. mulanjeensis from Mount Mulanje in Malawi and P. mutareensis from the Nyanga mountain range in the Eastern Highlands of Zimbabwe, based on mtDNA evidence. These three species can easily be distinguished morphologically. Potamonautes mutareensis shows a moderately arched right dactylus, a characteristic common in most smallbodied freshwater crab living in mountainous regions. This feature is absent in P. flavusjo sp. nov (since the right chelae is broken off), but the dactylus is not arched in any of the other specimens. In addition, the two species are also distinct on the basis of carapace colour, with P. flavusjo sp. nov. possessing a bright-yellow postfrontal crest margin and yellow margins of the carapace, whereas these features in P. mutareensis are all brown. Potamonautes mulanjeensis is a similar sized species (CWW = 34.81 mm) to P. flavusjo sp. nov. Neither of the two species sister to P. flavusjo sp. nov. have a burrowing lifestyle.

Superficially, P. flavusjo sp. nov. is morphologically similar to the two South African freshwater crab species that are semi-terrestrial: P. calcaratus and P. lividus . All three freshwater crab species are characterized by a vaulted carapace, which is an adaptation to a semiterrestrial lifestyle away from permanently flowing rivers and streams. In both P. lividus and P. calcaratus the dactylus of the right cheliped is arched, whereas in P. calcaratus the dactylus of the right chela is flattened, which is an adaptation for burrowing. Potamonautes calcaratus has a small but distinct tooth on the anterolateral margin of the carapace, a nearflat right cheliped, and a slate-black carapace. The carapace of P. lividus when alive is blue with a light-blue shine, whereas the chelipeds and limbs are orange or red. No carapace dentition is present in either P. lividus or P. flavusjo sp. nov.

In contrast, in P. flavusjo sp. nov. the major cheliped shows no special adaptation for a burrowing mode of life. Potamonautes lividus does not burrow to the same depths as P. flavusjo sp. nov. or P. calcaratus . All three of these species are ecologically distinct, with P. flavusjo sp. nov. being exclusively associated with peat soils in vlei areas on the Mpumalanga Highveld, where it occurs under grass and reed banks. Burrows of P. flavusjo sp. nov. are generally straight and vertical, and typically stretch up to 1 m into the peat soil; however, the burrow depth is dependent on the depth of the water table (S.R.D., pers. observ.). Burrows always have a single opening used for both entry and exit, with the crab generally occupying a small round chamber at the bottom of the burrow that is full of freshwater (pH 7.38, near neutral; conductivity 103 μS cm –1; temperature of the water at bottom of the burrow 14.6°C, recorded at the Iona Farm sample site in the district of Chrissiesmeer only). In contrast, P. lividus forms U-shaped burrows, <30 cm deep (G. Gouws, pers. comm.), and is endemic to hydromorphic peat swamp forest areas (comprosed of Barringtonia , Ficus , and Syzygium trees) in north-eastern KwaZulu- Natal ( Gouws et al., 2001). More recently a population of P. lividus was discovered at Dwessa Forest in the Eastern Cape province of South Africa, approximately 750 km from its previously known distribution range in KwaZulu-Natal (S.R.D., pers. observ.). Unpublished mtDNA sequence data reveal that the Eastern Cape and KwaZulu-Natal specimens are genetically nearly identical (S.R.D., pers. observ.). Potamonautes lividus has also been collected under decaying logs of wood in forested areas, particularly following episodes of heavy rains (S.R.D., pers. observ.). Potamonautes calcaratus is exclusive to the Kruger National Park in South Africa, although the species is also present in southern Mozambique and Zimbabwe ( Reed & Cumberlidge, 2004). Potamonautes calcaratus can typically be found around ephemeral pans where they burrow into the banks of the pans. A single burrow opening is present in this species, and the burrows can extend deep into the soil around the ephemeral pans.

Etymology: The name P. flavusjo sp. nov. is an arbitrary combination of two aspects. The species name takes ‘flavus’, Latin for yellow, as a reference to the distinct canary yellow postfrontal crest margin ( Fig. 6 ), whereas ‘jo’ is added in honour of Dr Johan Engelbrecht, recently deceased, for his unwavering dedication and commitment to freshwater research in the Mpumalanga province of South Africa, and for sending the authors the first female specimen of the species. The name is used as a noun in apposition.

Figures

Figure 6. Live image of a female Potamonautes flavusjo sp. nov., from Elandshoek, 1987 m a.s.l. (SAM A 48209), Mpumalanga province of South Africa, demonstrating the bright-yellow postfrontal crest margin. Photo taken by Gerhard Diedericks.

Figure 7. Potamonautes flavusjo sp. nov., male holotype (carapace length = 24.02 mm) Verloren Vallei Nature Reserve (site B), 2000 m a.s.l., 25°20′333″ S, 30°07′546″ E, Mpumalanga province of South Africa (SAM A 48203): A, whole animal, dorsal aspect; B, whole animal, ventral aspect; C, cephalothorax, frontal aspect. Scale bars: 10 mm. The right cheliped was broken off prior to capture.

Figure 8. Potamonautes flavusjo sp. nov., male holotype, Verloren Vallei Nature Reserve (site B), Mpumalanga province of South Africa (SAM A 48203). A, left gonopod 1, anterior view; B, left gonopod 1, posterior view; C, left gonopod 2, anterior view. Scale bars: 10 mm.